This proposal focuses on peripheral and mucosal cellular immune responses to HIV-1 in repeatedly exposed, persistently uninfected (ESN) women in Chennai, India. We hypothesize that women repeatedly exposed to HIV-1 via sexual contact might develop protective immune responses, including HIV-1-specific T-cells, and that development of such responses might be positively correlated with exposure frequency and viral load in the seropositive partner. Specific Aim 1: Establish and validate methods of detecting HIV-1-specific T-cell responses in peripheral blood and cervical cytobrush samples in the laboratory at YRG CARE, Chennai. These studies will be directed towards establishing basic research methods in cellular immunology, specifically the ELISPOT assay and cytokine flow cytometry (CFC). To establish and validate these methods, peripheral blood and mucosal samples (i.e., cervical cytobrush) will be analyzed from HIV-1-positive and low-risk seronegative women. Specific Aim 2: Using the assays established in Specific Aim 1, we will compare HIV-1 specific T cell responses in peripheral blood and/or cervicovaginal mucosa of ESN women with those from matched HIV positive women in a seroconcordant relationship and from HIV negative controls. We hypothesize that HIV-1-specific T-cells in cervicovaginal mucosa may be particularly relevant to protection from mucosal transmission, that the magnitude of cervical immunity in ESN women over time will fluctuate depending on frequency of exposure, and the magnitude of immune responses may be greater in mucosal tissues than in blood. Specific Aim 3: Assess the relationship between HIV-1-specific T-cell responses in ESN women with the semen and viral load of seropositive partners, as well as frequency of unprotected sex. [unreadable] [unreadable]